There are three types of Light Probes - Reflection Cube Map - Reflection Plane - Irradiance Volume #Reflection Probes The two first are, as the name suggests, to generate reflections in materials. They may seem useless at first because you can enable *Screen Space Reflections" in EEVEE render panel, however screen space reflections have limitations. They are very fast to generate, but [can only capture objects that are currently displayed in the viewport][1], that is inside the view fustrum. These probes allow calculation more complex and accurate types of reflection through use of a helper object. ##Reflection Plane As the name suggests are the most simple ones, suitable for mostly flat surfaces like mirrors, glass panes, floor reflections, or rainy pavements. On more complex objects they will probably generate weird results. It has a clipping distance that will limit which objects are visible in its reflections. Objects with reflective materials which are withing its range (the bounding box around it) will be influenced by what this plane "sees", benefiting from the the probe reflection map [![enter image description here][2]][2] ##Reflection Cube Map Similar to the plane this will generate a more complex reflection map suited for curving shapes. Unlike the plane though this is not a real time process and requires baking, specifically the *Bake Cubemap Only* option from the *Render Panel* in the *Properties Editor*. It also has slipping distances which affect what is reflected and what gets clipped away, and moving an object away from its influence radius also removes it from it's "effect". [![enter image description here][3]][3] #Irradiance Volume *Irradiance Volume* is a different kind of probe, it calculates indirect lighting and shadows. Real time rasterization engines like EEVEE although very advanced [can't really calculate indirect lighting by themselves][4], thus need a help calculating and storing this information. Irradiance Volume preform both these tasks by storing the indirect lighting information in a grid array of points, the resolution of which can be adjusts in its *Resolution XYZ* in *Object Data* Properties. Once again *Clipping* affects which objects are in range for calculation, and everything inside its volume gets influenced by the light calculation. Likewise, since this is potentially heavy calculation it requires baking from the render panel to show it's influence, the higher the XYZ resolution the denser the grid, the heavier the calculation thus slower process, with higher quality result. [![enter image description here][5]][5] Workflows: 1. Add probe object 2. Adjust position 3. Scale it so it encompasses all desired objects 4. Adjust clipping distances and grid density 5. Bake (from render panel for *Cube Maps* and *Irrandiance Volumes*) Here are the results of the various bake steps No Bake [![enter image description here][6]][6] Cube Maps only (no indirect lighting) [![enter image description here][7]][7] Bake indirect lighting [![enter image description here][8]][8] [1]: https://blender.stackexchange.com/questions/126602/screen-space-reflections-in-eevee [2]: https://i.sstatic.net/fZTi2.gif [3]: https://i.sstatic.net/iT1jp.gif [4]: https://blender.stackexchange.com/questions/123724/eevee-and-cycles-render-lighting-differences [5]: https://i.sstatic.net/jiQs5.gif [6]: https://i.sstatic.net/J7Jyw.png [7]: https://i.sstatic.net/9Y21X.png [8]: https://i.sstatic.net/j6z9m.jpg